ABSTRACT
Microzooplankton are ubiquitous organisms in aquatic systems that play multifaceted trophic roles, as they may act as bacterivores, herbivores, omnivores, nutrient recyclers and prey for metazoans. Given the prevalence of phototrophic plankton among primary producers, they have evolved preferentially toward an herbivore trophic mode, representing the main mortality factor for phytoplankton in most aquatic ecosystems. In addition, many microzooplankton species are able to photosynthesize which produces diverse effects on element budgets and ecosystem functioning. At the community level, microzooplankton interfere with carbon pumps by prolonging the permanence of nutrients in the sunlit ocean through remineralization processes, thus delaying the resource-limitation of their prey. Most observations suggest that microzooplankton communities will rapidly respond and adapt to climate change due to their fast generation time, their nutritional plasticity, and the enormous functional diversity contained in their genetic reservoir. Warming is expected to stimulate the growth and grazing of microzooplankton and given the differential thermal dependency of phototrophs relative to heterotrophs, the coupling between microzooplankton and phytoplankton will maximise in polar and subpolar regions. Considering the projected dominance of small prey in the future ocean, microzooplankton will constitute a trophic buffer through efficiently repackaging prey inaccessible to larger consumers.
